Expansible mandrels for use in driving or withdrawing tubular piles

ABSTRACT

Expansible mandrels are disclosed for use in driving or withdrawing tubular piles and the like, said mandrels comprising sections with a head connected to and joining their upper ends, and with at least one means below said head operable to vary the spacing of the mandrel sections between pile-entering and pilegripping relationships. The operating means include a plurality of members within the mandrel and spaced lengthwise thereof, flexible means in trained engagement with the members and operable on a pull thereon in a predetermined direction to move the members in predetermined directions, and force-transmitting connections between the members and the mandrel sections to transmit opposite transverse forces thereto urging them into one of said relationships on such movement of the members. The pull on the flexible means is established in effecting either one or both operative relationships by power operated means.

United States Patent [1 1 Guild et al.

EXPANSIBLE MANDRELS FOR USE IN DRIVING OR WITHDRAWING TUBULAR PILES Inventors: Charles L. Guild, 7 Stone Tower Ln., Barrington, RI. 02806; Willard B. Goodman, P.O. Box 62, Newport, Oreg. 97365 Filed: June 10, 1971 Appl. No.: 151,786

Related U.S. Application Data Continuation-impart of Ser. No. 824,631, May 14, 1969, abandoned.

U.S. Cl 61/53.!2, 242/72, 254/188 Int. Cl. E02d 7/30 Field of Search 6l/53.72, 53.7; 242/72;1

References Cited UNITED STATES PATENTS 5/1964 Thornley 61/5172 8/1966 Guild 11/1961 Rusche 11/1965 Binnings 61/53.72

WIIIIIIIIIIIflMIM [451 Apr. 16, 1974 Primary Examiner-Jacob Shapiro [5 7] ABSTRACT Expansible mandrels are disclosed for use in driving or withdrawing tubular piles and the like, said mandrels comprising sections with a head connected to and joining their upper ends, and with at least one means below said head operable to vary the spacing of the mandrel sections between pile-entering and pilegripping relationships. The operating means include a plurality of members within the mandrel and spaced lengthwise thereof, flexible means in trained engagement with the members and operable on a pull thereon in a predetermined direction to move the members in predetermined directions, and forcetransmitting connections between the members and the mandrel sections to transmit opposite transverse forces thereto urging them into one of said relationships on such movement of the members. The pull on the flexible means is established in effecting either one or both operative relationships by power operated means.

111 Claims, 75 Drawing Figures 32 r 34 4T 7 I {O i PAIENTE mu 6 2914 I sum 10 or '36 A Nmm v. mom mp mU mhm i mi "MEMTEBAPR 16 mm UMM 

1. An expansible mandrel for use in driving or withdrawing tubular members such as piles, tubes, pipes and the like, said mandrel comprising sections, a head connected to and joining the upper ends of the sections, said sections being shaped and dimensioned so that they may move towards and away from each other to have a first relationship in which the mandrel may be entered in a tubular member of a predetermined cross sectional size and shape and a second relationship in which the sections grip interior surfaces of the entered tubular member, and at least one means operable to effect such movement of the sections, said means including a flexible element extending lengthwise of the interior of the mandrel and a plurality of units within and spaced lengthwise along the interior of said mandrel, each unit including a member, and said units being so incorporated in said mandrel relative to its sections and the flexible element being so trained relative to their members that on a pull on the flexible element in one direction, said units subject said sections to opposite transverse forces that are operable to urge the sections relative to each other into one of said relationships.
 2. The expansible mandrel of claim 1 in which said one relationship is the pile-entering relationship.
 3. The expansible mandrel of claim 1 in which said one relationship is the pile-gripping relationship.
 4. The expansible mandrel of claim 1 in which the members are arranged in two series and the trained engagement of the flexible means therewith moves the members in opposite directions.
 5. The expansible mandrel of claim 1 and second flexible means common to the members and in such trained engagement therewith that the members are moved, in response to a pull thereon, in a direction opposite to that resulting from a pull on the first named flexible means, to transmit opposite transverse forces on the mandrel sections urging them into the other of their relationships.
 6. The expansible mandrel of claim 1 in which a fluid pressure operated unit is supported by the mandrel within its upper part and connected to the flexible means to effect an upward pull thereon.
 7. The expansible mandrel of claim 6 in which the head includes a receiver attachable to a hammer and provided with a marginal flange and axial neck to which the fluid pressure operated unit is connected, a cap connecting the upper end of the mandrel sections through which the neck extends, and an annular member fitting the neck and interposed between the flange and the cap, a series of keepers overlying the flange and resting on the annular member, and bolt means connecting the cap and the keepers through the annular member.
 8. The expansible mandrel of claim 7 in which the bolt means includes, adjacent their ends, complementally concave-convex portions.
 9. The expansible mandrel of claim 8 in which the head includes a neck entrant of the upper end of the mandrel, a first backing part fixed on the neck, a second backing part pivotally connected to the fluid pressure operated unit, and lashing interconnecting the backing parts.
 10. The expansible mandrel of claim 5 in which corresponding ends of both flexible means are anchored to a mandrel section, a fluid pressure operated, piston-cylinder unit is supported by the mandrel between the sections adjacent the head, the other end of one flexible means connected to the unit to be subjected to a pull when the unit is operated and the mandrel having a laterally disposed opening adjacent the head through which the other end of the other flexible means extends to enable it to be connected to a power device located externally of and above the mandrel capable of exerting an operating pull thereon.
 11. The expansible mandrel of claim 10 in which the mandrel opening through which the other flexible means extends has a pair of rotatable elements spaced lengthwise of each other through which said other flexible means is trained, the two rotatable elements being disposed to define the opening.
 12. The expansible mandrel of claim 1 and a toggle joint connecting the mandrel sections at their lower ends and disposed, when actuated in a predetermined direction to urge the lower ends into one of the two relationships, an actuating member between the sections, one end of the actuating member being connected to the toggle joint, a sheave connected to the other end of the actuating member, and the flexible means is an element trained about the sheave to exert a pull thereon in the predetermined direction.
 13. The expansible mandrel of claim 12 and resilient means between the mandrel sections yieldably urging the bottom ends of the mandrel sections into the other relationship.
 14. The expansible mandrel of claim 12 in which the flexible element is the element in trained engagement with the members of the operating means.
 15. The expansible mandrel of claim 12 in which the relationship into which the mandrel sections are urged by the flexible element is the pile-gripping relationship.
 16. The expansible mandrel of claim 15 and stop means operable to limit the extent to which the mandrel sections may be moved by the flexible element.
 17. The expansible mandrel of claim 16 in which the actuating member has a transverse plate intermediate its ends, and the stop means comprises at least one stop carried by at least one of the mandrel sections for engagement with the plate.
 18. The expansible mandrel of claim 17 in which each mandrel section includes internal reinforcements adjacent its edges marginally confining the plate of the actuating member and the stop means comprises one stop anchored to each reinforcement.
 19. The expansible mandrel of claim 12 in which the actuating member includes a pivot between its ends.
 20. The expansible mandrel of claim 12 in which the toggle joint includes a pair of links, a pivotal connection between each link and a mandrel section, the attaching means is in the form of a plate, and a pivotal connection between each link and the plate, one on each side of the mandrel axis.
 21. The expansible mandrel of claim 20 in which the pivotal connections between the links and the plate are closer together than the pivotal connections between the links and the mandrel sections.
 22. The expansible mandrel of claim 20 in which the pivotal connections between the links and the mandrel section in the pile-entering relationship thereof are spaced apart a distance less than the distance between the pivotal connections between the links and the plate, each pivotal connection between the links and the mandrel sections including a pivot pin, the plate having a pair of holes, one for each pivot pin and so dimensioned and disposed tHat its margins function as a section-spreading cam until the links are parallel.
 23. The expansible mandrel of claim 1 and a toggle joint connecting the bottom ends of the mandrel sections and including an actuator and a sheave carried by the actuator, the flexible means is an element trained about the sheave with a course in trained engagement with the members including portions on both sides of the mandrel axis and with a course extending upwardly lengthwise of the mandrel, the sheave being diagonally disposed to position the last named course wholly within one mandrel section but at one side of the portions of the other course that are within that section.
 24. The expansible mandrel of claim 23 in which the course that is wholly within one mandrel section is anchored to the upper end thereof and power operated means are connected to the upper end of the other course.
 25. The expansible mandrel of claim 1, and springs spaced lengthwise of the mandrel and attached to the mandrel sections and operable to yieldably urge the mandrel sections into their other relationship.
 26. The expansible mandrel of claim 14 in which the relationship established by the springs is the first or pile-gripping relationship.
 27. The expansible mandrel of claim 14 in which the relationship established by the springs is the second or pile-entering relationship.
 28. The expansible mandrel of claim 14 in which each mandrel section includes lengthwise reinforcements, the reinforcements of the two sections include transversely aligned sockets spaced lengthwise of the mandrel, and the springs are confined in the transversely aligned sockets.
 29. The expansible mandrel of claim 1 in which the members are sheaves, the force-transmitting connections are toggle joints and each includes means connecting a sheave thereto, and the flexible means is an element trained about the sheaves to effect a joint actuating pull thereon.
 30. The expansible mandrel of claim 29 in which the toggle joints are arranged in oppositely disposed pairs establishing two series of members and the flexible element is trained about the sheaves of each pair of toggle joints to urge them towards each other on a pull on the element to urge the mandrel sections into one of said relationships.
 31. The expansible mandrel of claim 30 in which the distance between the toggle joints increases towards the upper end of the mandrel.
 32. The expansible mandrel of claim 30 and a second flexible element trained about the proximate sheaves of proximate pairs of toggle joints to urge them towards each other on a pull on the second element to urge the mandrel sections into the other of said relationships.
 33. The expansible mandrel of claim 29 in which the connecting means is an actuating member.
 34. The expansible mandrel of claim 33 and vertically spaced stops fixed on the mandrel sections and engageable by opposite ends of the actuating member to limit their movement lengthwise of the mandrel.
 35. The expansible mandrel of claim 33 in which there are a pair of transversely spaced side supports for each toggle joint secured in each mandrel section, the support of each pair having transversely aligned pockets at one end opening through their edges that are proximate to the other pair of supports and extending downwardly and outwardly towards their other ends, the toggle joint includes at least one pair of arms, a pin for each arm and supported in the appropriate pockets, and a pin connecting the other ends of the arms and the actuating member.
 36. The expansible mandrel of claim 33 in which each toggle joint includes side supports carried by the mandrel sections and engageable by the actuator to limit the extent to which it may swing.
 37. The expansible mandrel of claim 33 in which there is a pivoted connection between each toggle joint and the actuator and each connecting means includes stops limiting the extent to which each actuator may swing.
 38. The expansible mandrel of claim 32 in which a bottom Toggle joint connects the bottom ends of the mandrel sections, the bottom toggle joint includes an actuator extending towards the other end of the mandrel and has a sheave, the flexible element by which the pile-gripping relationship of the mandrel section is established extends downwardly in the mandrel and about the sheave of the bottom toggle joint and then about both sheaves of each pair of toggle joints, and the flexible element by which the pile-entering relationship of the mandrel sections is established is first trained downwardly about the sheave of the bottom toggle joint, then about the proximate sheave of the proximate pair of toggle joints, and then again about the sheave of the bottom toggle joint.
 39. The expansible mandrel of claim 1 in which the members are arranged in two series, one series of each mandrel section, the members being arranged in groups in which the members of one series alternate with those of the other series, the groups being spaced lengthwise of the mandrel, the trained engagement of the flexible means is with the members of each group in succession, and the members are so disposed transversely of the mandrel sections and so dimensioned that the trained engagement of the flexible means is sinuous whereby the sections are forced into one of said relationships as a pull on the flexible means straightens it.
 40. The expansible mandrel of claim 39 in which the portion of each member of the series of each mandrel section with which the flexible means is in trained engagement extends into the other section and the relationship resulting from a straightening pull is the pile-gripping relationship.
 41. The expansible mandrel of claim 39 in which the portion of each member of the series of each mandrel section engaged by the flexible means is within its mandrel section and the relationship resulting from a straightening pull is the pile-entering relationship.
 42. The expansible mandrel of claim 39 in which the members are rotatable with the members of each series dimensioned to provide portions in both mandrel sections.
 43. The expansible mandrel of claim 42 in which the axes of the rotatable members of each series are located above the plane inclusive of the edges of the mandrel sections of that series.
 44. The expansible mandrel of claim 39 and second flexible means trained successively about the members in a manner opposite to that of the first named flexible means whereby a pull on the second flexible means forces the mandrel sections into the other of said relationships.
 45. The expansible mandrel of claim 39 in which the numbers of members in each group decreases towards the upper end of the mandrel.
 46. The expansible mandrel of claim 39 in which the distance between the groups increases towards the upper end of the mandrel.
 47. The expansible mandrel of claim 1 in which the relationship established by the pull on the flexible means is the first or pile-gripping relationship and the members are spaced and arranged lengthwise of the mandrel and relative to each other to provide an expanding force distribution that is at a maximum adjacent the bottom end of the mandrel.
 48. The expansible mandrel of claim 47 in which the spacing of the members results in a pile-gripping relationship and the members are spaced and arranged to provide an expanding force distribution that is at a maximum adjacent the bottom end of the mandrel.
 49. The expansible mandrel of claim 47 in which the spacing of the members results in a force being applied and the trained engagement of the flexible member is such that said force is progressively in time from the bottom of the mandrel to the upper end thereof.
 50. The expansible mandrel of claim 1 in which each mandrel section is arcuate in cross section and includes a pair of transversely spaced, internal, lengthwise reinforcements establishing a central channel, each unit being within the channels of both sections.
 51. The expansible mandrel of claim 50 in which each reinforcemenT is right angular in cross section.
 52. The expansible mandrel of claim 50 in which the reinforcements extend substantially the full length of the mandrel sections.
 53. The expansible mandrel of claim 50 in which each unit includes a carriage seated in one channel with portions entrant of the other channel and fitting between the reinforcements thereof.
 54. The expansible mandrel of claim 53 in which each unit is anchored to the reinforcements between which it is seated.
 55. The expansible mandrel of claim 39 in which each mandrel section is arcuate in cross section and includes a reinforcement in the form of a diaphragm plate extending substantially the full length of the mandrel adjacent its edge and each diaphragm plate has openings for the members of each group.
 56. The expansible mandrel of claim 55 in which each member includes a mount seated through one of its openings and anchored to the appropriate diaphragm.
 57. The expansible mandrel of claim 55 in which each opening is dimensioned to accommodate all the members of the appropriate group, and means interconnect corresponding members of the groups under the diaphragms and the interconnecting means are secured to the upper and bottom ends of the mandrel sections.
 58. The expansible mandrel of claim 57 in which each member includes a carriage and each mandrel section has a pair of mounts extending lengthwise of each opening and welded therein adjacent its edges, the mounts for each opening including transversely spaced pairs of bars defining seats, each slidably receiving and confining the carriage of a member of one series, and the pairs of bars are spaced lengthwise from each other to accommodate the members of the other series.
 59. The expansible mandrel of claim 1 in which each mandrel section includes a pair of lengthwise, laterally spaced members to which the force-transmitting connections are attached, a lengthwise connecting member welded to and connecting the pair of laterally spaced members of each section, and a marginal member welded to each of the pair of laterally spaced members of each section, the connecting and marginal members all being arcuate with respect to a common center, and the portions of each section that are the junction between the arcuate members and the pair of laterally spaced members also being substantially arcuate with respect to said center.
 60. The expansible mandrel of claim 59 in which the portions of each of the pair of laterally spaced members of each section that is exposed within that section are rectangular in cross section.
 61. The expansible mandrel of claim 60 in which each of the pair of laterally spaced members of each section includes an outer portion separating the welds between the marginal and connecting members.
 62. The expansible mandrel of claim 60 in which the marginal members of each section have inturned, transversely aligned flanges.
 63. The expansible mandrel of claim 1 in which the operating means extends substantially the full length of the mandrel.
 64. The expansible mandrel of claim 1 in which there is a plurality of operating means, each spaced lengthwise of the mandrel and each of the operating means includes a fluid pressure operated unit within and supported by the mandrel to which its flexible element is connected and by which an operating pull is effected.
 65. The expansible mandrel of claim 64 in which said one relationship of each of the operating means is the pile-gripping relationship and each of the operating means includes means connected to the mandrel sections and operable to urge the mandrel sections into their pile-entering relationship.
 66. The expansible mandrel of claim 64 in which each fluid pressure unit includes a stem having predetermined travel, and each of the means urging the mandrel sections into their pile-entering relationship includes a pair of arms pivotally connected to the stem of the appropriate one of the units to travel with the flexible element and each arm includes a connEction with an appropriate one of the mandrel sections that is slidable while said stem is exerting said pull but is seated before the stem has fully returned then to urge the mandrel sections into their pile-entering relationships.
 67. The expansible mandrel of claim 39 in which a fluid pressure operated unit is supported by the mandrel between upper end portions of the mandrel sections and includes a stem, a sheave is rotatably supported by the stem, one of the mandrel sections includes a sheave mounted therein in a fixed position between the uppermost group and the sheave of the unit, and the flexible means is anchored at one end to the bottom of one mandrel section and its upper end is trained about the sheave of the unit and anchored to the fixed sheave.
 68. The expansible mandrel of claim 1 and a cannister within said mandrel and supported thereby, said cannister including sections, one for each mandrel section, the force-transmitting connections including the cannister sections.
 69. The expansible mandrel of claim 68 in which the members of the operating means are within the cannister and connected to the cannister sections.
 70. The expansible mandrel of claim 68 in which the lower end of each section of the cannister is supported by a seat on the appropriate one of the mandrel sections and each mandrel section includes a cannister-centering part overlying the upper end of a cannister section, and a resiliently yieldable bumper is disposed between each said upper end and the overlying part.
 71. The expansible mandrel of claim 68 and means connecting each cannister section to the appropriate one of the mandrel sections to prevent the cannister section from turning relative to the mandrel section.
 72. The expansible mandrel of claim 71 in which each mandrel section has a bottom plate and each cannister section has a bottom plate which seats on the bottom plate of the appropriate mandrel section, and a key and a keying connection between the appropriate mandrel and cannister plates.
 73. The expansible mandrel of claim 39 in which the members include carriers, means interconnect the carriers of each series of members, and suspending means connect each series of interconnected carriers to an appropriate one of the mandrel sections with the carriers disposed for force-transmitting engagement therewith.
 74. The expansible mandrel of claim 73 in which the mandrel sections include bottom plates and the suspending means are connected to the upper ends of the mandrel sections and the bottom plates.
 75. The expansible mandrel of claim 74 in which the connections of the suspending means with the bottom plates are resilient.
 76. The expansible mandrel of claim 73 in which the interconnecting means are flexible.
 77. The expansible mandrel of claim 73 in which the interconnecting means are links pivotally connected to the carriers.
 78. The expansible mandrel of claim 73 in which the interconnecting means include mounts for the members of each group, each member of each group being connected to its mount for movement transversely of the mandrel.
 79. The expansible mandrel of claim 1 in which each mandrel section includes a bottom plate, and there is a key and keyway connection between the bottom plates.
 80. The expansible mandrel of claim 39 in which each member of both series of each group of members protrudes from one of the mandrel sections into the other mandrel section and a carrier seated within the first named mandrel section in a force-transmitting relationship therewith, and a connection between said member and carrier.
 81. The expansible mandrel of claim 80 in which each carrier also includes retaining means spaced from the member supported by that carrier and disposed to retain the flexible means in desired relation thereto when the tension thereon is relaxed.
 82. The expansible mandrel of claim 80 in which each member is rotatably supported by its carrier.
 83. The expansible mandrel of claim 80 in which each member Is arcuate and presents a fixed surface with which the flexible means is in sliding contact.
 84. The expansible mandrel of claim 80 in which the connection between each member and its carrier enables the member to move relative thereto transversely of the mandrel.
 85. The expansible mandrel of claim 80 in which each member is a sheave and the flexible means is a cable.
 86. The expansible mandrel of claim 80 in which each member is spherical and the flexible means is a roller chain whose rollers are concave.
 87. The expansible mandrel of claim 80 in which each member includes a spherical rim having an annular groove receiving the flexible means.
 88. The expansible mandrel of claim 82 in which each member is a sprocket and the flexible means is a chain.
 89. The expansible mandrel of claim 82 in which each member has a pair of peripheral channels and the flexible means comprise a pair of chains of the crane chain type, one for each channel and anchored to a mandrel section in such a manner that their links define an X in their trained engagement with the members, each channel including a central V-shaped crest subdividing it for the reception of the two series of links of an appropriate one of the chains.
 90. The expansible mandrel of claim 89 in which each of the corresponding links of the two chains are longitudinally offset.
 91. The expansible mandrel of claim 82 in which each member is a pulley and the flexible means is a belt.
 92. The expansible mandrel of claim 82 in which each member is a multi-grooved sheave and the flexible means is a series of wire ropes.
 93. The expansible mandrel of claim 82 in which the members and their connections are self-aligning.
 94. The expansible mandrel of claim 82 in which the members are of magnetic stock, the carriers are of non-magnetic stock, and the flexible means are magnetically responsive.
 95. The expansible mandrel of claim 84 in which each carrier includes a socket and a compression spring within each socket urges the member supported thereby towards the other mandrel section.
 96. The expansible mandrel of claim 81 in which the connection is a resiliently flexible pin.
 97. The expansible mandrel of claim 84 in which each carrier includes a socket and the member supported thereby includes a portion slidably entered within the socket.
 98. The expansible mandrel of claim 95 in which each member is spherical, the carrier includes side portions confining that member and each mandrel section also includes means extending lengthwise confining the members of the other section against escape from their carriers and providing guides for the flexible means.
 99. The expansible mandrel of claim 39 in which each member of both series of each group of members protrudes from the mandrel section with which it is in force-transmitting relationship into the other mandrel section, the end members of each group are secured to the first named mandrel section and each intermediate member is free to move relative thereto in a direction lengthwise of the mandrel.
 100. The expansible mandrel of claim 83 in which each mandrel section, in the zone of each of the connecting means, includes a pair of lengthwise supports, pairs of transversely aligned ears, each ear attached to an appropriate one of said supports and protruding beyond the edges of the section to which it is attached, and each member is a sheave and includes a pin supported by a pair of ears.
 101. The expansible mandrel of claim 100 in which the lengthwise supports of each mandrel section have transversely aligned lengthwise channels and frames, each frame including a pair of ears and marginal portions slidably confined by the channels.
 102. The expansible mandrel of claim 101 in which the channels are straight.
 103. The expansible mandrel of claim 101 in which the channels are arcuate.
 104. The expansible mandrel of claim 100 in which the ears have transversely aligned bores dimensioned to slidably receive the sheave pin and thE sheave pin slidably supports its sheave, the bores being spaced to enable a sheave pin to be inserted therethrough with the frame connected to the supports, the supports of each mandrel section including transversely aligned pin stops confining the ends of a pin of a sheave connected to the other mandrel section from objectionable axial movement.
 105. The expansible mandrel of claim 100 in which each pair of ears has transversely aligned bores, a bushing is fitted in each bore and slidably receives the ends of a sheave pin, each sheave is slidably supported by its sheave pin, the bores of each ear are located to be partly blocked by the supports to which they are attached and partly blocked, on the assembled mandrel, by the supports of the other section, one bushing including sections so dimensioned that with the pin in support of its sheave and with one pin end seated in the other bushing, and with the other mandrel section spaced to expose the portion of the bores it blocks when the mandrel is in use, the bushing sections can be inserted one at a time into the bore and turned to support the other pin end.
 106. The expansible mandrel of claim 105 in which each bushing has a shoulder at the outer end of its pin-receiving bore.
 107. An expansible mandrel for use in driving or withdrawing tubular piles and the like, said mandrel comprising sections, a head connected to and joining the upper ends of said sections, and means operable to vary the spacing between pile-entering and pile-gripping relationships, said means including portions in force-applying relationship with said sections and means operable to provide an expanding force distribution on said portions that is at a maximum adjacent the bottom end of the mandrel and decreases towards the upper end to provide a substantially constant force in opposition to the pressure of the surrounding earch which increases in depth.
 108. The expansible mandrel of claim 107 in which the expanding force is applied progressively in time from the botttom of the mandrel to the upper end thereof.
 109. An expansible mandrel for use in driving or withdrawing tubular piles and the like, said mandrel comprising sections, a head, means connecting the upper ends of the sections to the head in a fixed spaced-apart relationship that biases the sections below the connecting means towards each other to establish a normal pile-entering relationship, and means between the sections and operable to force said sections apart into a pile-gripping relationship.
 110. The expansible mandrel of claim 109 in which the connecting means include surfaces that are in mutual contact when the mandrel sections are connected to the head, one of the mutually engageable surfaces being inclined relative to the mandrel axis and to the other surface so that when the surfaces are in mutual contact, the mandrel sections are biased inwardly towards each other.
 111. The expansible mandrel of claim 109 in which the head includes a flange, each mandrel section includes a flange at its upper end, an inwardly tapering wedge section is interposed between each section flange and the head flange, and clamping bolts interconnect the section flanges to the head flanges through the appropriate wedge section. 